Control Frame Handling By a Provider Backbone Bridge

ABSTRACT

A method and Bridge in a Provider Backbone Bridge Network (PBBN) for enabling frames from a Higher Layer Entity attached alternatively to a Provider Instance Port (PIP) on an I-Component of a Backbone Edge Bridge or to a Customer Backbone Port on a B-Component of the Backbone Edge Bridge, to reach an intended entity in the PBBN. A Virtual Instance Port Service Access Point (VIP SAP) is configured for every VIP and every Higher Layer Entity configured on the I-Component. An Enhanced VIP Port Connectivity function utilizes the VIP SAP to tunnel customer-initiated Layer 2 Control Protocols (L2CPs). A Special Multiplexed SAP handles the frames of the Higher Layer Entity, and is assigned an I-SID value that is universally recognized to identify the L2CPs. A Service Instance Multiplex Entity utilizes the Special Multiplexed SAP to transfer frames between the PIP or the Customer Backbone Port and the entity inside the PBBN.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/884,817 filed Jan. 12, 2007.

TECHNICAL FIELD

This invention relates to communication networks. More particularly, andnot by way of limitation, the invention is directed to a system, method,and Bridge for handling control frames in a Provider Backbone BridgeNetwork (PBBN). The method enables frames from a Higher Layer Entityattached to the Bridge to reach an intended entity in the PBBN.

BACKGROUND

The draft IEEE Standard for Local and Metropolitan Area Networks:Virtual Bridged Local Area Networks (IEEE P802.1Q-2006/D0.1) specifiesthat a VLAN aware Bridge includes a Media Access Control (MAC) RelayEntity that interconnects the Bridge's Ports, at least two Ports, andhigher layer entities, including at least a Spanning Tree ProtocolEntity. The MAC Relay Entity handles the media access method-independentfunctions of relaying frames among Bridge Ports, filtering frames, andlearning filtering information. The MAC Relay Entity uses the EnhancedInternal Sublayer Service (EISS) provided by each Bridge Port.

Each Bridge Port can also function as an end station providing one ormore instances of the MAC Service. Each instance of the MAC Service isprovided to a distinct Logical Link Control (LLC) Entity that supportsprotocol identification, multiplexing, and demultiplexing for PDUtransmission and reception by one or more higher layer entities.

Bridges identify Layer 2 Control Protocols (L2CPs) by the “type” fieldfollowing the MAC addresses in the protocol frames. The destinationaddress of a L2CP frame determines the span of connectivity of the frameand thus to which ports it is delivered. Thus, the relay function withina bridge forwards or filters the frame according to the destinationaddress, regardless of the type. A given protocol only operates onframes containing a “type” field corresponding to that given protocol;however the protocol may also use other criteria to determine whatoperation, if any, is to be performed. These criteria may include thedestination address, VLAN ID, and/or fields within the MAC Service DataUnit (SDU). How these criteria are used in determining how to process aframe is protocol dependent. The determination by the protocol entitiesof whether or not to process a frame is independent of whether the frameis forwarded or filtered by the relay.

The connectivity of the Higher Layer Entities to the other bridgeentities as currently specified in Section 8.5 of IEEE Std 802.1Q,cannot meet the demands required by complex types of ports such as theports on a Provider Backbone Edge Bridge (BEB). The BEB ports aredescribed in the draft IEEE Standard for Local and Metropolitan AreaNetworks—Virtual Bridged Local Area Networks—Amendment 06: ProviderBackbone Bridges (IEEE P802.1ah/D3.3, December 2006). Frames initiatedby or destined to Higher Layer Entities that are attached on a ProviderInstance Port (PIP) or a Customer Backbone Port (CBP) would not reachtheir intended peer entities if they are not properly tagged. Inaddition, BEBs do not have the capability of tunneling, discarding, orpeering the L2CPs initiated by the attached customer networks. Currentspecifications also fail to provide a mechanism that would allow HigherLayer Entities to communicate over an External Network-to-NetworkInterface (E-NNI). Enhancements are needed to the Bridge PortConnectivity functionality described in IEEE Standard 802.1Q in order toaddress these issues.

What is needed in the art is a system, method, and Bridge that helpsalleviate the problems associated with the issues outlined above. Thepresent invention provides such a system, method, and Bridge.

SUMMARY

The present invention provides a generic mechanism for tunneling L2CPframes initiated by attached customer networks, and it provides amechanism that allows Higher Layer Entities to communicate over anE-NNI. The invention provides advanced handling of control frames forcustomer systems attached to a Provider Backbone Bridge Network (PBBN),and provides a mechanism for exchanging control protocols with operatorsof other PBBNs.

In one embodiment, the present invention is directed to a method ofhandling control frames in a Provider Backbone Bridge in a ProviderBackbone Bridge Network (PBBN). The method enables frames from a HigherLayer Entity attached alternatively to a Provider Instance Port on anI-Component of a Backbone Edge Bridge or to a Customer Backbone Port ona B-Component of the Backbone Edge Bridge, to reach an intended entityin the PBBN. The method includes the steps of configuring a VirtualInstance Port (VIP) Service Access Point (SAP) for every VIP and everyHigher Layer Entity configured on the I-Component; and utilizing the VIPSAP to tunnel customer-initiated Layer 2 Control Protocols (L2CPs). Themethod also includes the steps of configuring a Special Multiplexed SAPfor the frames of the Higher Layer Entity, wherein the SpecialMultiplexed SAP is assigned a Service Instance ID (I-SID) value that isuniversally recognized to identify the L2CPs; and utilizing the SpecialMultiplexed SAP to transfer frames between the Provider Instance Port orthe Customer Backbone Port and the entity inside the PBBN.

In another embodiment, the present invention is directed to a Bridge ina PBBN for enabling frames from a Higher Layer Entity attachedalternatively to a Provider Instance Port on an I-Component of aBackbone Edge Bridge or to a Customer Backbone Port on a B-Component ofthe Backbone Edge Bridge, to reach an intended entity in the PBBN. TheBridge includes a VIP SAP configured for every VIP and every HigherLayer Entity configured on the I-Component; and an Enhanced VIP PortConnectivity function for utilizing the VIP SAP to tunnelcustomer-initiated L2CPs. The Bridge also includes a Special MultiplexedSAP for handling the frames of the Higher Layer Entity, said SpecialMultiplexed SAP having an I-SID value that is universally recognized toidentify the L2CPs; and a Service Instance Multiplex Entity forutilizing the Special Multiplexed SAP to transfer frames between theProvider Instance Port or the Customer Backbone Port and the entityinside the PBBN.

In another embodiment, the present invention is directed to a system ina PBBN for enabling frames from a Higher Layer Entity attachedalternatively to a Provider Instance Port on an I-Component of aBackbone Edge Bridge or to a Customer Backbone Port on a B-Component ofthe Backbone Edge Bridge, to reach an intended entity in the PBBN. Thesystem includes a plurality of interconnected Bridges, each of whichincludes at least two ports, a Media Access Control (MAC) Relay Entitythat interconnects the Bridge's ports, and at least one Higher LayerEntity. Each Bridge also includes a VIP SAP configured for every VIP andevery Higher Layer Entity configured on the I-Component, and an EnhancedVIP Port Connectivity function for utilizing the VIP SAP to tunnelcustomer-initiated L2CPs. Each Bridge also includes a SpecialMultiplexed SAP for handling the frames of the Higher Layer Entity,wherein the Special Multiplexed SAP is assigned an I-SID value that isuniversally recognized to identify the L2CPs. A Service InstanceMultiplex Entity utilizes the Special Multiplexed SAP to transfer framesbetween the Provider Instance Port or the Customer Backbone Port and theentity inside the PBBN.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the essential features of the invention will bedescribed in detail by showing preferred embodiments, with reference tothe attached figures in which:

FIG. 1 illustrates an exemplary embodiment of the present invention whenproviding a VIP SAP for two Higher Layer Entities and for an EnhancedVIP Port Connectivity function on an I-Component;

FIG. 2 illustrates an exemplary embodiment of the present invention whenproviding a Special Multiplexed SAP for frames of Higher Layer Entitiesthat are initiated by a PIP on an I-component or a CBP on a B-componentand are required to reach a device inside a PBBN; and

FIG. 3 is a flow chart of an exemplary embodiment of the method of thepresent invention.

DETAILED DESCRIPTION

The present invention enables Higher Layer Entities attached to aProvider Instance Port on an I-Component, or to a Customer Backbone Porton a B-Component, to reach intended entities in a Provider BackboneBridged Network. In particular, the present invention achieves thetunneling of customer-initiated L2CPs by introducing a Virtual InstancePort (VIP) Service Access Point (SAP) for every VIP and every HigherLayer Entity configured on the I-Component. The invention achieves thecommunication of a PIP or a CBP with an entity inside the PBBN byutilizing a Special Multiplexed SAP, which is assigned a specificService Instance ID (I-SID) value, for example 0xFFFFFF.

An I-Component is a component of a BEB which performsencapsulation/decapsulation of Provider Bridge frames. An I-Component islocated at the edge of a PBBN. It consists of an S-VLAN-aware bridgecomponent where each IEEE802.1 Customer Instance Port can recognizeservice VLAN tags (STAGs) and where each IEEE802.1 PIP canencapsulate/decapsulate frames inside an Ethernet frame which usesbackbone MAC addresses and a Service Instance TAG (I-TAG). A B-Componentis a component of a BEB which performs frame forwarding over a PBBN. AB-Component is located at the edge of a PBBN. It consists of anS-VLAN-aware bridge component where each IEEE802.1 Provider BackbonePort can recognize backbone VLAN tags (B-TAGs).

Two sets of Higher Layer SAPs are configured on a PIP: (1) a VIP SAP isprovided for every Higher Layer Entity and every VIP port on theI-Component; and (2) a Special Multiplexed SAP is provided for frames ofHigher Layer entities that are initiated by a PIP on an I-component or aCBP on a B-component and are required to reach a device inside the PBBN.The VIP SAPs are actually related to the Virtual Instance Ports internalto the PIP, while the Special Multiplexed SAPs are also applicable tothe Customer Backbone Ports on a B-Component.

FIG. 1 illustrates an exemplary embodiment of the present invention whenproviding a VIP SAP 10 for two Higher Layer Entities 11 a, 11 b and foran Enhanced VIP Port Connectivity function 12 on an I-Component 13.Frames of Higher Layer Entities that are initiated by a PIP 14 and arerequired to reach Customer Networks placed on the opposite side of anintervening PBBN are encapsulated in the same way as data frames. Anexample of such a usage is that of Provider Bridged BPDUs that aretransmitted transparently through the PBBN. The Enhanced VIP PortConnectivity function 12 provides multiple copies of each frame destinedto the VIP: one copy for the EISS and one copy for each Higher LayerEntity attached to the VIP.

Each Indication provided by the VIP EISS access point 15 for the PIP 14results in a corresponding Indication with identical parameters at a VIPEISS 16 supporting a MAC Relay Entity 17 and the VIP SAPs 10 supportingthe Higher Layer Entities 11 a, 11 b. Each Request from the VIP EISSaccess point 16 supporting the MAC Relay Entity results in acorresponding Indication with identical parameters at the VIP SAP accesspoints 10 for the Higher Layer Entities and in a corresponding Requestwith identical parameters at the VIP EISS access point 15 for the PIP.Each Request from the VIP SAP access point 10 supporting a Higher LayerEntity results in a corresponding Indication with identical parametersat the VIP EISS access point 16 for the MAC Relay Entity, and at otheraccess points for Higher Layer Entities, and in a corresponding Requestwith identical parameters at the access point for the LAN 15.

Frames injected from the LLC Higher Layer SAPs 18 that are S-VLANuntagged utilize a EISS Multiplex Entity 19 as described in thecorresponding subclause of the draft IEEE Standard for Local andMetropolitan Area Networks—Virtual Bridged Local Area Networks—Amendment05: Connectivity Fault Management (IEEE P802.1ag/D7.1, November 2006).

FIG. 2 illustrates an exemplary embodiment of the present invention whenproviding a Special Multiplexed SAP 21 for frames of Higher LayerEntities 22 that are initiated by a PIP on an I-component or a CBP on aB-component and are required to reach a device inside the PBBN. EachSpecial Multiplexed SAP is assigned an I-SID value that is universallyrecognized to identify the Layer 2 Control Protocols (L2CPs), forexample I-SID 0xFFFFFF. Upon receipt of an Indication from an ISS SAP23, a Service Instance Multiplex Entity 24 examines the initial octetsof the mac_service_data_unit parameter for a valid service instance tagheader. If the initial octets contain a valid short service instance tagheader and the I-SID value matches the value assigned to the multiplexedSAPs for L2CPs, then this tag header is removed from themac_service_data_unit and the Indication is presented to the L2CP SAP21. Otherwise the Indication is presented unmodified to the single PIPISS SAP 25.

Upon receipt of a Request from the L2CP SAP 21, the Service InstanceMultiplex Entity 24 modifies the mac_service_data_unit parameter byprepending a short service instance tag header using the I-SID valueassigned (for example, 0xFFFFFF). The Request is then presented to thesingle ISS SAP 23 of the Service Instance Multiplex Entity. A Request orIndication received from the PIP ISS SAP 25 is presented unmodified tothe single ISS SAP 23.

In this manner, the present invention provides a generic mechanism fortunneling L2CP frames initiated by attached customer networks, and itprovides a mechanism that allows Higher Layer Entities to communicateover an External Network-to-Network Interface. The invention providesadvanced handling of control frames for customer systems attached to aProvider Backbone Bridge Network, and provides a mechanism forexchanging control protocols with operators of other PBBNs.

FIG. 3 is a flow chart of an exemplary embodiment of the method of thepresent invention. At step 31, a VIP SAP 10 is configured for every VIPand Higher Layer Entity 11 a, 11 b , 22 on the I-Component 13. At step32, the VIP SAP is utilized to tunnel customer-initiated L2CPs. At step33, a Special Multiplexed SAP is configured with a universallyrecognized I-SID for Higher Layer Entity frames to identify L2CPs. Atstep 34, the Special Multiplexed SAP is utilized to transfer framesbetween the PIP and Customer Backbone Port and the entity in the PBBN.

Although preferred embodiments of the present invention have beenillustrated in the accompanying drawings and described in the foregoingDetailed Description, it is understood that the invention is not limitedto the embodiments disclosed therein, but is defined by the followingclaims.

1. A method of handling control frames in a Provider Backbone Bridge ina Provider Backbone Bridge Network (PBBN), said method enabling framesfrom a Higher Layer Entity attached alternatively to a Provider InstancePort (PIP) on an I-Component of a Backbone Edge Bridge or to a CustomerBackbone Port on a B-Component of the Backbone Edge Bridge, to reach anintended entity in the PBBN, said method comprising the steps of:configuring a Virtual Instance Port Service Access Point (VIP SAP) forevery VIP and every Higher Layer Entity configured on the I-Component;utilizing the VIP SAP to tunnel customer-initiated Layer 2 ControlProtocols (L2CPs); configuring a Special Multiplexed SAP for the framesof the Higher Layer Entity, said Special Multiplexed SAP having aService Instance ID (I-SID) value that is universally recognized toidentify the L2CPs; and utilizing the Special Multiplexed SAP totransfer frames between the PIP or the Customer Backbone Port and theentity inside the PBBN.
 2. The method as recited in claim 1, wherein thestep of configuring the Special Multiplexed SAP includes assigning tothe Special Multiplexed SAP, a special I-SID value.
 3. The method asrecited in claim 1, wherein the step of utilizing the VIP SAP to tunnelcustomer-initiated L2CPs includes the steps of: encapsulating the framesof the Higher Layer Entity that are initiated by the PIP and arerequired to reach Customer Networks placed on an opposite side of thePBBN; and providing multiple copies of each frame destined to the VIP,wherein one copy is provided for the Enhanced Internal Sublayer Service(EISS) provided by each Bridge Port, and one copy is provided for eachHigher Layer Entity attached to the VIP.
 4. The method as recited inclaim 3, wherein the step of utilizing the VIP SAP to tunnelcustomer-initiated L2CPs also includes the steps of: receiving by anEnhanced VIP Port Connectivity function, an Indication from a VIP EISSaccess point for the PIP; and in response to the Indication, providingby the Enhanced VIP Port Connectivity function, a correspondingIndication with identical parameters at a VIP EISS supporting a MACRelay Entity and the VIP SAP supporting the Higher Layer Entity.
 5. Themethod as recited in claim 4, wherein the step of utilizing the VIP SAPto tunnel customer-initiated L2CPs also includes the steps of: receivingby the Enhanced VIP Port Connectivity function, a Request from the VIPEISS supporting a MAC Relay Entity; and in response to the Request:providing by the Enhanced VIP Port Connectivity function, acorresponding Indication with identical parameters at the VIP SAPsupporting the Higher Layer Entity; and providing by the Enhanced VIPPort Connectivity function, a corresponding Request with identicalparameters at the VIP EISS access point for the PIP.
 6. The method asrecited in claim 5, wherein the step of utilizing the VIP SAP to tunnelcustomer-initiated L2CPs also includes the steps of: receiving by theEnhanced VIP Port Connectivity function, a Request from the VIP SAPsupporting the Higher Layer Entity; and in response to the Request:providing by the Enhanced VIP Port Connectivity function, acorresponding Indication with identical parameters at the EISS accesspoint for the MAC Relay Entity; providing by the Enhanced VIP PortConnectivity function, a corresponding Indication with identicalparameters at any VIP SAPs supporting other Higher Layer Entities; andproviding by the Enhanced VIP Port Connectivity function, acorresponding Request with identical parameters at the access point fora local area network, LAN.
 7. The method as recited in claim 1, whereinthe step of utilizing the Special Multiplexed SAP to transfer framesincludes the steps of: receiving by a Service Instance Multiplex Entity,an Indication from an Internal Sublayer Service (ISS) SAP; anddetermining by the Service Instance Multiplex Entity, whether theinitial octets of a mac_service_data_unit parameter include a validservice instance tag header; if the initial octets include a validservice instance tag header: removing the tag header from themac_service_data_unit; and providing the Indication to a L2CP SAP; andif the initial octets do not include a valid service instance tagheader, providing the Indication unmodified to a PIP ISS SAP.
 8. Themethod as recited in claim 7, wherein the step of utilizing the SpecialMultiplexed SAP to transfer frames also includes the steps of: receivingby the Service Instance Multiplex Entity, a Request from the L2CP SAP;modifying the mac_service_data_unit parameter by prepending a shortservice instance tag header using the I-SID value assigned to theSpecial Multiplexed SAP; and providing the Request to the ISS SAP of theService Instance Multiplex Entity.
 9. The method as recited in claim 8,wherein the step of utilizing the Special Multiplexed SAP to transferframes also includes the steps of: receiving by the Service InstanceMultiplex Entity, a Request or Indication from the PIP ISS SAP; andproviding the Request or Indication unmodified to the ISS SAP.
 10. ABridge in a Provider Backbone Bridge Network (PBBN) for enabling framesfrom a Higher Layer Entity attached alternatively to a Provider InstancePort (PIP) on an I-Component of a Backbone Edge Bridge or to a CustomerBackbone Port on a B-Component of the Backbone Edge Bridge, to reach anintended entity in the PBBN, said Bridge comprising: a Virtual InstancePort Service Access Point (VIP SAP) configured for every VIP and everyHigher Layer Entity configured on the I-Component; an Enhanced VIP PortConnectivity function for utilizing the VIP SAP to tunnelcustomer-initiated Layer 2 Control Protocols (L2CPs); a SpecialMultiplexed SAP for handling the frames of the Higher Layer Entity, saidSpecial Multiplexed SAP having a Service Instance ID (I-SID) value thatis universally recognized to identify the L2CPs; and a Service InstanceMultiplex Entity for utilizing the Special Multiplexed SAP to transferframes between the PIP or the Customer Backbone Port and the entityinside the PBBN.
 11. The Bridge as recited in claim 10, wherein theSpecial Multiplexed SAP is assigned a special I-SID value.
 12. TheBridge as recited in claim 10, wherein the Enhanced VIP PortConnectivity function includes: means for encapsulating the frames ofthe Higher Layer Entity that are initiated by the PIP and are requiredto reach Customer Networks placed on an opposite side of the PBBN; andmeans for providing multiple copies of each frame destined to the VIP,wherein one copy is provided for the Enhanced Internal Sublayer Service(EISS) provided by each Bridge Port, and one copy is provided for eachHigher Layer Entity attached to the VIP.
 13. The Bridge as recited inclaim 12, wherein the Enhanced VIP Port Connectivity function alsoincludes: means for receiving an Indication from a VIP EISS access pointfor the PIP; and means responsive to the Indication, for providing bythe Enhanced VIP Port Connectivity function, a corresponding Indicationwith identical parameters at a VIP EISS supporting a MAC Relay Entityand the VIP SAP supporting the Higher Layer Entity.
 14. The Bridge asrecited in claim 12, wherein the Enhanced VIP Port Connectivity functionalso includes: means for receiving a Request from the VIP EISSsupporting a MAC Relay Entity; and means responsive to the Request: forproviding a corresponding Indication with identical parameters at theVIP SAP supporting the Higher Layer Entity; and for providing acorresponding Request with identical parameters at the VIP EISS accesspoint for the PIP.
 15. The Bridge as recited in claim 12, wherein theEnhanced VIP Port Connectivity function also includes: means forreceiving a Request from the VIP SAP supporting the Higher Layer Entity;and means responsive to the Request: for providing a correspondingIndication with identical parameters at the EISS access point for theMAC Relay Entity; for providing a corresponding Indication withidentical parameters at any VIP SAPs supporting other Higher LayerEntities; and for providing a corresponding Request with identicalparameters at the access point for a local area network, LAN.
 16. TheBridge as recited in claim 10, wherein the Service Instance MultiplexEntity includes: means for receiving an Indication from an InternalSublayer Service (ISS) SAP; and means for determining whether theinitial octets of a mac_service_data_unit parameter include a validservice instance tag header; means responsive to a determination thatthe initial octets include a valid service instance tag header: forremoving the tag header from the mac_service_data_unit; and forproviding the Indication to a L2CP SAP; and means responsive to adetermination that the initial octets do not include a valid serviceinstance tag header, for providing the Indication unmodified to a PIPISS SAP.
 17. The Bridge as recited in claim 10, wherein the ServiceInstance Multiplex Entity also includes: means for receiving a Requestfrom the L2CP SAP; means for modifying the mac_service_data_unitparameter by prepending a short service instance tag header using theI-SID value assigned to the Special Multiplexed SAP; and means forproviding the Request to the ISS SAP of the Service Instance MultiplexEntity.
 18. The Bridge as recited in claim 10, wherein the ServiceInstance Multiplex Entity includes: means for receiving a Request orIndication from the PIP ISS SAP; and means for providing the Request orIndication unmodified to the ISS SAP.
 19. A system in a ProviderBackbone Bridge Network (PBBN) for enabling frames from a Higher LayerEntity attached alternatively to a Provider Instance Port (PIP) on anI-Component of a Backbone Edge Bridge or to a Customer Backbone Port ona B-Component of the Backbone Edge Bridge, to reach an intended entityin the PBBN, said system comprising: a plurality of interconnectedBridges, each Bridge including: at least two ports; a Media AccessControl (MAC) Relay Entity that interconnects the Bridge's ports; and atleast one Higher Layer Entity; wherein each Bridge also includes: aVirtual Instance Port Service Access Point (VIP SAP) configured forevery VIP and every Higher Layer Entity configured on the I-Component;an Enhanced VIP Port Connectivity function for utilizing the VIP SAP totunnel customer-initiated Layer 2 Control Protocols; a SpecialMultiplexed SAP for handling the frames of the Higher Layer Entity, saidSpecial Multiplexed SAP having a Service Instance ID (I-SID) value thatis universally recognized to identify the L2CPs; and a Service InstanceMultiplex Entity for utilizing the Special Multiplexed SAP to transferframes between the PIP or the Customer Backbone Port and the entityinside the PBBN.